Environmentally Resistant Ballistic Composite Based on a Nitrile Rubber Binder

ABSTRACT

Ballistic resistant fabrics and articles that retain superior ballistic resistance performance after exposure to liquids such as sea water and organic solvents, such as gasoline and other petroleum-based products. The fabrics are formed from high performance fibers coated with a nitrile rubber binder polymer having an acrylonitrile content of from about 15 wt. % to about 50 wt. %, and are optionally coated with a binder that is a blend of a nitrile rubber and a fluorine-containing material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to ballistic resistant articles having excellentresistance to deterioration due to liquid exposure. More particularly,the invention pertains to ballistic resistant fabrics and articles thatretain their superior ballistic resistance performance after exposure toliquids such as seawater and organic solvents, such as gasoline andother petroleum-based products.

2. Description of the Related Art

Ballistic resistant articles containing high strength fibers that haveexcellent properties against projectiles are well known. Articles suchas bullet resistant vests, helmets, vehicle panels and structuralmembers of military equipment are typically made from fabrics comprisinghigh strength fibers. High strength fibers conventionally used includepolyethylene fibers, aramid fibers such as poly(phenylenediamineterephthalamide), graphite fibers, nylon fibers, glass fibers and thelike. For many applications, such as vests or parts of vests, the fibersmay be used in a woven or knitted fabric. For other applications, thefibers may be encapsulated or embedded in a polymeric matrix material toform woven or non-woven rigid or flexible fabrics. Preferably each ofthe individual fibers forming the fabrics of the invention aresubstantially coated or encapsulated by the binder (matrix) material.

Various ballistic resistant constructions are known that are useful forthe formation of hard or soft armor articles such as helmets, panels andvests. For example, U.S. Pat. Nos. 4,403,012, 4,457,985, 4,613,535,4,623,574, 4,650,710, 4,737,402, 4,748,064, 5,552,208, 5,587,230,6,642,159, 6,841,492, 6,846,758, all of which are incorporated herein byreference, describe ballistic resistant composites which include highstrength fibers made from materials such as extended chain ultra-highmolecular weight polyethylene. These composites display varying degreesof resistance to penetration by high-speed impact from projectiles suchas bullets, shells, shrapnel and the like.

For example, U.S. Pat. Nos. 4,623,574 and 4,748,064 disclose simplecomposite structures comprising high strength fibers embedded in anelastomeric matrix. U.S. Pat. No. 4,650,710 discloses a flexible articleof manufacture comprising a plurality of flexible layers comprised ofhigh strength, extended chain polyolefin (ECP) fibers. The fibers of thenetwork are coated with a low modulus elastomeric material. U.S. Pat.Nos. 5,552,208 and 5,587,230 disclose an article and method for makingan article comprising at least one network of high strength fibers and amatrix composition that includes a vinyl ester and diallyl phthalate.U.S. Pat. No. 6,642,159 discloses an impact resistant rigid compositehaving a plurality of fibrous layers which comprise a network offilaments disposed in a matrix, with elastomeric layers there between.The composite is bonded to a hard plate to increase protection againstarmor piercing projectiles.

Hard or rigid body armor provides good ballistic resistance, but can bevery stiff and bulky. Accordingly, body armor garments, such asballistic resistant vests, are preferably formed from flexible or softarmor materials. However, while such flexible or soft materials exhibitexcellent ballistic resistance properties, they also generally exhibitpoor resistance to liquids, including fresh water, seawater and organicsolvents, such as petroleum, gasoline, gun lube and other solventsderived from petroleum. This is problematic because the ballisticresistance performance of such materials is generally known todeteriorate when exposed to or submerged in liquids. Further, while ithas been known to apply a protective film to a fabric surface to enhancefabric durability and abrasion resistance, as well as water or chemicalresistance, these films add weight to the fabric. Accordingly, it wouldbe desirable in the art to provide soft, flexible ballistic resistantmaterials that perform at acceptable ballistic resistance standardsafter being contacted with or submerged in a variety of liquids, andalso have superior durability without the use of a protective surfacefilm in addition to a polymeric binder coating. The present inventionprovides a solution to this need.

Few conventional binder materials, commonly referred to in the art aspolymeric “matrix” materials, are capable of providing all the desiredproperties discussed herein. Nitrile rubber polymers are desirable inother arts due to their resistance to dissolution, penetration and/ortranspiration by sea water and resistance to dissolution, penetrationand/or transpiration by one or more organic solvents, such as dieselgasoline, non-diesel gasoline, gun lube, petroleum and organic solventsderived from petroleum. It has been discovered that nitrile rubber ornitrile rubber-containing coatings advantageously contribute to theretention of the ballistic resistance properties of a ballisticresistant fabric after prolonged exposure to potentially harmfulliquids, eliminating the need for a protective surface film to achievesuch benefits, while maintaining good flexibility. Excellent ballisticand environmental properties have also been achieved when coatingballistic resistant fibrous materials with a composition comprising ablend of a nitrile rubber or nitrile rubber-containing polymer and afluorine-containing polymer, which includes fluorine-containingoligomers and fluorine-containing resins.

SUMMARY OF THE INVENTION

The invention provides a non-woven ballistic resistant fabric comprisinga plurality of fibers arranged in an array, said fibers being united andforming a fabric, said fibers having a tenacity of about 7 g/denier ormore and a tensile modulus of about 150 g/denier or more; and saidfibers having a polymeric binder material thereon which comprises anitrile rubber polymer, said binder being resistant to dissolution,penetration and/or transpiration by water and resistant to dissolution,penetration and/or transpiration by one or more organic solvents,wherein the nitrile rubber polymer has an acrylonitrile content of fromabout 15 wt % to about 50 wt % and which polymeric binder materialcomprises from about 2% to about 50% by weight of the fabric.

The invention also provides a method of producing a ballistic resistantfabric, the method comprising either step I) or step II), wherein:

-   I) applying a polymeric binder material onto a plurality of fibers    and thereafter forming a non-woven fabric from said fibers; said    fibers having a tenacity of about 7 g/denier or more and a tensile    modulus of about 150 g/denier or more; wherein said polymeric binder    material comprises a nitrile rubber polymer, said binder being    resistant to dissolution, penetration and/or transpiration by water    and resistant to dissolution, penetration and/or transpiration by    one or more organic solvents, wherein the nitrile rubber polymer has    an acrylonitrile content of from about 15 wt % to about 50 wt % and    which polymeric binder material comprises from about 2% to about 50%    by weight of the fabric; or-   II) organizing a plurality of fibers into at least one fiber layer,    thereafter combining the at least one fiber layer with a polymeric    binder material to form a non-woven fabric; said fibers having a    tenacity of about 7 g/denier or more and a tensile modulus of about    150 g/denier or more; wherein said polymeric binder material    comprises a nitrile rubber polymer, said binder being resistant to    dissolution, penetration and/or transpiration by water and resistant    to dissolution, penetration and/or transpiration by one or more    organic solvents, wherein the nitrile rubber polymer has an    acrylonitrile content of from about 15 wt % to about 50 wt % and    which polymeric binder material comprises from about 2% to about 50%    by weight of the fabric.

The invention further provides a polymer composition comprising a blendof at least one a fluorine-containing material and at least one nitrilerubber terpolymer.

DETAILED DESCRIPTION OF THE INVENTION

The ballistic resistant materials and articles of the invention arecharacterized by retaining superior ballistic penetration resistanceafter exposure to water, particularly seawater, and organic solvents,particularly solvents derived from petroleum such as gasoline. Ballisticresistant fabrics and articles herein are formed from high strengthfibers that are coated with a polymeric binder material which comprisesa nitrile rubber polymer and is resistant to dissolution, penetrationand/or transpiration by water, such as sea water, and resistant todissolution, penetration and/or transpiration by one or more organicsolvents, such as diesel gasoline, non-diesel gasoline, gun lube,petroleum and organic solvents derived from petroleum.

For the purposes of the invention, articles that have superior ballisticpenetration resistance describe those which exhibit excellent propertiesagainst deformable projectiles and against penetration of fragments,such as shrapnel. The articles of the invention exhibit particularlyhigh retention of ballistic performance against fragments, specifically16-grain Right Circular Cylinder (RCC) fragments, after exposure toliquids. For the purposes of the present invention, a “fiber” is anelongate body the length dimension of which is much greater than thetransverse dimensions of width and thickness. The cross-sections offibers for use in this invention may vary widely. They may be circular,flat or oblong in cross-section. Accordingly, the term fiber includesfilaments, ribbons, strips and the like having regular or irregularcross-section. They may also be of irregular or regular multi-lobalcross-section having one or more regular or irregular lobes projectingfrom the linear or longitudinal axis of the fibers. It is preferred thatthe fibers are single lobed and have a substantially circularcross-section.

In the preferred embodiment of the invention, the ballistic resistantfabrics of the invention are non-woven fabrics which comprise aplurality of overlapping, non-woven fibrous plies that are consolidatedinto a single-layer, monolithic element. In this embodiment, each plycomprises an arrangement of non-overlapping fibers that are aligned in aunidirectional, substantially parallel array. This type of fiberarrangement is known in the art as a “unitape” (unidirectional tape) andis referred to herein as a “single ply”. As used herein, an “array”describes an orderly arrangement of fibers or yams, and a “parallelarray” describes an orderly parallel arrangement of fibers or yams. Afiber “layer” describes a planar arrangement of woven or non-wovenfibers or yams including one or more plies. As used herein, a“single-layer” structure refers to monolithic structure composed of oneor more individual fiber plies that have been consolidated into a singleunitary structure. By “consolidating” it is meant that the polymericbinder material, together with each fiber ply are combined into a singleunitary layer. Consolidation can occur via drying, cooling, heating,pressure or a combination thereof. The term “composite” refers toconsolidated combinations of fibers with the polymeric binder material.

A preferred non-woven fabric of the invention includes a plurality ofstacked, overlapping plies (plurality of unitapes) wherein the parallelfibers of each single ply (unitape) are positioned orthogonally (0°/90°)to the parallel fibers of each adjacent single ply relative to thelongitudinal fiber direction of each single ply. The stack ofoverlapping non-woven fiber plies is consolidated under heat andpressure, or by adhering the polymeric resin composition coatings ofindividual fiber plies, to form a single-layer, monolithic element whichhas also been referred to in the art as a single-layer, consolidatednetwork where a “consolidated network” describes a consolidated (merged)combination of fiber plies with a polymeric binder material. A polymericbinder material as used herein is also referred to in the art as apolymeric matrix composition. The terms “polymeric binder material” and“polymeric matrix composition” are used interchangeably herein, anddescribe a material that binds the fibers together by way of theiradhesive characteristics or after being subjected to well known heatand/or pressure conditions.

As is conventionally known in the art, excellent ballistic resistance isachieved when individual fiber plies are cross-plied such that the fiberalignment direction of one ply is rotated at an angle with respect tothe fiber alignment direction of another ply. Most preferably, the fiberplies are cross-plied orthogonally at 0° and 90° angles, but adjacentplies can be aligned at virtually any angle between about 0° and about90° with respect to the longitudinal fiber direction of another ply. Forexample, a five ply non-woven structure may have plies oriented at a0°/45°/90°/45°/0° or at other angles. Such rotated unidirectionalalignments are described, for example, in U.S. Pat. Nos. 4,457,985;4,748,064; 4,916,000; 4,403,012; 4,623,573; and 4,737,402.

Most typically, non-woven fabrics include from 1 to about 6 plies, butmay include as many as about 10 to about 20 plies as may be desired forvarious applications. The greater the number of plies translates intogreater ballistic resistance, but also greater weight. Accordingly, thenumber of fiber plies forming a fabric or an article of the inventionvaries depending upon the ultimate use of the fabric or article. Forexample, in body armor vests for military applications, in order to forman article composite that achieves a desired 1.0 pound per square footareal density (4.9 kg/m²), a total of about 20 plies (or layers) toabout 60 individual plies (or layers) may be required, wherein theplies/layers may be woven, knitted, felted or non-woven fabrics (withparallel oriented fibers or other arrangements) formed from thehigh-strength fibers described herein. In another embodiment, body armorvests for law enforcement use may have a number of plies/layers based onthe National Institute of Justice (NIJ) Threat Level. For example, foran NIJ Threat Level IIIA vest, there may be a total of 22 plies/layers.For a lower NIJ Threat Level, fewer plies/layers may be employed.

Consolidated non-woven fabrics may be constructed using well-knownmethods, such as by the methods described in U.S. Pat. No. 6,642,159,the disclosure of which is incorporated herein by reference. Further,the fiber plies of the invention may alternately comprise yarns ratherthan fibers, where a “yarn” is a strand consisting of multiplefilaments. Non-woven fiber plies may alternately comprise feltedstructures which are formed using conventionally known techniques,comprising fibers in random orientation instead of parallel arrays.Articles of the invention may also comprise combinations of wovenfabrics, non-woven fabrics formed from unidirectional fiber plies andnon-woven felt fabrics.

In another embodiment of the invention, the ballistic resistant fabricsof the invention comprise woven fabrics. Woven fabrics may be formedusing techniques that are well known in the art using any fabric weave,such as plain weave, crowfoot weave, basket weave, satin weave, twillweave and the like. Plain weave is most common, where fibers are woventogether in an orthogonal 0°/90° orientation. In another embodiment, ahybrid structure may be assembled where one both woven and non-wovenfabrics are combined and interconnected, such as by consolidation. Priorto weaving, the individual fibers of each woven fabric material may ormay not be coated with the polymeric binder material of the invention ina similar fashion as the non-woven fabrics.

The fibers forming the fabrics of the invention comprise high-strength,high tensile modulus fibers. As used herein, a “high-strength, hightensile modulus fiber” is one which has a preferred tenacity of at leastabout 7 g/denier or more, a preferred tensile modulus of at least about150 g/denier or more, and preferably an energy-to-break of at leastabout 8 J/g or more, each both as measured by ASTM D2256. As usedherein, the term “denier” refers to the unit of linear density, equal tothe mass in grams per 9000 meters of fiber or yarn. As used herein, theterm “tenacity” refers to the tensile stress expressed as force (grams)per unit linear density (denier) of an unstressed specimen. The “initialmodulus” of a fiber is the property of a material representative of itsresistance to deformation. The term “tensile modulus” refers to theratio of the change in tenacity, expressed in grams-force per denier(g/d) to the change in strain, expressed as a fraction of the originalfiber length (in/in).

Particularly suitable high-strength, high tensile modulus fibermaterials include polyolefin fibers, particularly extended chainpolyolefin fibers, such as highly oriented, high molecular weightpolyethylene fibers, particularly ultra-high molecular weightpolyethylene fibers and ultra-high molecular weight polypropylenefibers. Also suitable are aramid fibers, particularly para-aramidfibers, polyamide fibers, polyethylene terephthalate fibers,polyethylene naphthalate fibers, extended chain polyvinyl alcoholfibers, extended chain polyacrylonitrile fibers, polybenzazole fibers,such as polybenzoxazole (PBO) and polybenzothiazole (PBT) fibers, liquidcrystal copolyester fibers. Each of these fiber types is conventionallyknown in the art.

In the case of polyethylene, preferred fibers are extended chainpolyethylenes having molecular weights of at least 500,000, preferablyat least one million and more preferably between two million and fivemillion. Such extended chain polyethylene (ECPE) fibers may be grown insolution spinning processes such as described in U.S. Pat. Nos.4,137,394 or 4,356,138, which are incorporated herein by reference, ormay be spun from a solution to form a gel structure, such as describedin U.S. Pat. Nos. 4,551,296 and 5,006,390, which are also incorporatedherein by reference. A particularly preferred fiber type for use in theinvention are polyethylene fibers sold under the trademark SPECTRA® fromHoneywell International Inc. SPECTRA® fibers are well known in the artand are described, for example, in U.S. Pat. Nos. 4,623,547 and4,748,064.

Also particularly preferred are aramid (aromatic polyamide) orpara-aramid fibers. Such are commercially available and are described,for example, in U.S. Pat. No. 3,671,542. For example, usefulpoly(p-phenylene terephthalamide) filaments are produced commercially byDuPont corporation under the trademark of KEVLAR®. Also useful in thepractice of this invention are poly(m-phenylene isophthalamide) fibersproduced commercially by DuPont under the trademark NOMEX®, fibersproduced commercially by Teijin under the trademark TWARON®; aramidfibers produced commercially by Kolon Industries, Inc. of Korea underthe trademark Heracron®; p-aramid fibers SVM™ and Rusar™ which areproduced commercially by Kamensk Volokno JSC of Russia and Armos™p-aramid fibers produced commercially by JSC Chim Volokno of Russia.

Suitable polybenzazole fibers for the practice of this invention arecommercially available and are disclosed for example in U.S. Pat. Nos.5,286,833, 5,296,185, 5,356,584, 5,534,205 and 6,040,050, each of whichare incorporated herein by reference. Suitable liquid crystalcopolyester fibers for the practice of this invention are commerciallyavailable and are disclosed, for example, in U.S. Pat. Nos. 3,975,487;4,118,372 and 4,161,470, each of which is incorporated herein byreference.

Suitable polypropylene fibers include highly oriented extended chainpolypropylene (ECPP) fibers as described in U.S. Pat. No. 4,413,110,which is incorporated herein by reference. Suitable polyvinyl alcohol(PV-OH) fibers are described, for example, in U.S. Pat. Nos. 4,440,711and 4,599,267 which are incorporated herein by reference. Suitablepolyacrylonitrile (PAN) fibers are disclosed, for example, in U.S. Pat.No. 4,535,027, which is incorporated herein by reference. Each of thesefiber types is conventionally known and widely commercially available.

The other suitable fiber types for use in the present invention includeglass fibers, fibers formed from carbon, fibers formed from basalt orother minerals, rigid rod fibers such as M5® fibers, and combinations ofall the above materials, all of which are commercially available. Forexample, the fibrous plies may be formed from a combination of SPECTRA®fibers and Kevlar® fibers. M5® fibers are rigid rod fibers comprisingpyridobisimidazole-2,6-diyl (2,5-dihydroxy-p-phenylene) and aremanufactured by Magellan Systems International of Richmond, Va. and aredescribed, for example, in U.S. Pat. Nos. 5,674,969, 5,939,553,5,945,537, and 6,040,478, each of which is incorporated herein byreference. Specifically preferred fibers include M5® fibers,polyethylene SPECTRA® fibers, aramid Kevlar® fibers and aramid TWARON®fibers. The fibers may be of any suitable denier, such as, for example,50 to about 3000 denier, more preferably from about 200 to 3000 denier,most preferably from about 650 to about 1500 denier.

The most preferred fibers for the purposes of the invention are eitherhigh-strength, high tensile modulus extended chain polyethylene fibersor high-strength, high tensile modulus para-aramid fibers. As statedabove, a high-strength, high tensile modulus fiber is one which has apreferred tenacity of about 7 g/denier or more, a preferred tensilemodulus of about 150 g/denier or more and a preferred energy-to-break ofabout 8 J/g or more, each as measured by ASTM D2256. In the preferredembodiment of the invention, the tenacity of the fibers should be about15 g/denier or more, preferably about 20 g/denier or more, morepreferably about 25 g/denier or more and most preferably about 30g/denier or more. The fibers of the invention also have a preferredtensile modulus of about 300 g/denier or more, more preferably about 400g/denier or more, more preferably about 500 g/denier or more, morepreferably about 1,000 g/denier or more and most preferably about 1,500g/denier or more. The fibers of the invention also have a preferredenergy-to-break of about 15 J/g or more, more preferably about 25 J/g ormore, more preferably about 30 J/g or more and most preferably have anenergy-to-break of about 40 J/g or more.

These combined high strength properties are obtainable by employingwell-known processes. U.S. Pat. Nos. 4,413,110, 4,440,711, 4,535,027,4,457,985, 4,623,547 4,650,710 and 4,748,064 generally discuss theformation of preferred high strength, extended chain polyethylene fibersemployed in the present invention. Such methods, including solutiongrown or gel fiber processes, are well known in the art. Methods offorming each of the other preferred fiber types, including para-aramidfibers, are also conventionally known in the art, and the fibers arecommercially available.

In accordance with the invention, each of the fibers present in thewoven or non-woven fabrics of the invention have one or more surfaces,and the surfaces of the fibers are at least partially coated with apolymeric binder material that is resistant to dissolution, penetrationand/or transpiration by water, and resistant to dissolution by one ormore organic solvents. Generally, a coating of a polymeric bindermaterial is necessary to efficiently merge, i.e. consolidate, aplurality of fiber plies. Most preferably, the outer surface of eachfiber is substantially coated with said water and organic solventresistant polymeric binder material such that preferably 100% of thesurface area of each individual fiber is covered by said polymericbinder material. Where the fabrics comprise a plurality of yarns, eachfiber forming a single strand of yarn is preferably coated with thepolymeric binder material.

As stated above, the fibers comprising the ballistic resistant fabricsare coated with a polymeric binder material, which is also commonlyreferred to in the art as a polymeric matrix material. The polymericbinder material includes one or more components and facilitates theconsolidation, or merging together, of the fibers and fiber plies (i.e.multiple unitapes). The surfaces of each of the fibers forming saidfibrous layers are at least partially coated with a polymeric matrixmaterial, and each of the fibers forming the fabrics of the inventionare preferably substantially coated by the binder material.

The fibers of the invention are coated with a binder material thatcomprises a nitrile rubber polymer, preferably an uncured(non-crosslinked) nitrile rubber. Cured or crosslinked nitrile rubbershave a higher modulus than uncured nitrile rubbers and, accordingly, arestiffer than uncured materials, which is a concern in some soft bodyarmor applications. Nitrile rubber polymers are particularly desirablebecause they achieve the desired resistance to water, e.g. salt water,and organic solvents such as gasoline, while imparting good peelstrength and flexibility to the fabrics, both of which are indicationsof excellent durability. Nitrile rubber polymers are a family ofunsaturated copolymers of acrylonitrile and butadiene and many differenttypes are available having different properties. For example, thedesired resistance to organic solvents such as oil and gasoline may becontrolled and balanced with other properties, such as resistance toextreme temperatures, by regulating the acrylonitrile content of thenitrile rubber versus the butadiene content. Due to its polarity, anitrile rubber having a higher acrylonitrile content has betterresistance to oils and gasoline than nitrile rubbers with loweracrylonitrile content, and also increases tensile strength. Nitrilerubbers having a lower acrylonitrile content also exhibit goodresistance to oils and gasoline, though not as good as highacrylonitrile content polymers, but exhibit excellent flexibility andresilience, while high acrylonitrile content polymers exhibit higherstiffness and lower flexibility. For the present invention, it isimportant to strike a balance between the acrylonitrile and butadienedepending on the type of ballistic resistant fabric desired. In general,the nitrile rubber binder (or the nitrile rubber component of thebinder) has an acrylonitrile content of from about 15 wt. % to about 50wt. %. For soft armor applications, the nitrile rubber preferably has anacrylonitrile content of from about 15 wt. % to about 30 wt. %, morepreferably from about 20 wt. % to about 30 wt. %. For the formation offlexible, soft armor articles, the nitrile rubber preferably has a lowtensile modulus, particularly an initial tensile modulus measured atabout 6,000 psi (41.4 MPa) or less at 37° C. according to ASTM D638testing procedures. Preferably, the initial tensile modulus of thenitrile rubber for flexible, soft armor is about 4,000 psi (27.6 MPa) orless, more preferably about 2400 psi (16.5 MPa) or less, more preferably1200 psi (8.23 MPa) or less, and most preferably is about 500 psi (3.45MPa) or less. The glass transition temperature (Tg) of the nitrilerubber is preferably less than about 0° C., more preferably the lessthan about −40° C., and most preferably less than about −50° C. Thenitrile rubber also has a preferred elongation to break of at leastabout 50%, more preferably at least about 100% and most preferably hasan elongation to break of at least about 300%.

For hard armor applications, the nitrile rubber preferably has apreferred acrylonitrile content of from about 31 wt. % to about 50 wt.%, more preferably from about 40 wt. % to about 50 wt. %. Nitrile rubberbinders with a high acrylonitrile content generally have a highertensile modulus than low acrylonitrile materials and accordingly areparticularly well suited for rigid armor applications. Also, crosslinkednitrile rubbers have a higher tensile modulus than non-crosslinkedrubbers. There are at least three distinct crosslinking mechanismsspecifically for nitrile rubber, one more appropriate for hard armor(ZnO) and two for soft armor (sulfur and peroxide). These distinctmechanisms may also be combined or manipulated if desired. Lower modulusnitrile rubber-based composites are suited for a wider range of uses,while the higher modulus materials are more appropriate for theproduction of rigid and hard armor applications. As used hereinthroughout, the term tensile modulus means the modulus of elasticity asmeasured by ASTM 2256 for a fiber and by ASTM D638 for a polymericcomposition material.

In preferred embodiments of the invention, the nitrile rubber polymerscomprise nitrile rubber terpolymers comprising an acrylonitrile monomer,a butadiene monomer and another monomer component, such as N-methylolacrylamide or a carboxylic acid, such as methacrylic acid. Preferablythe nitrile rubber comprises a carboxylated nitrile rubber (XNBR)terpolymer. A preferred XNBR terpolymer preferably comprises from about0.1 weight % to about 20 weight % of the carboxylic acid monomer, morepreferably from about 1 wt. % to about 10 wt. % and most preferably fromabout 1 wt. % to about 5 wt. % of the carboxylic acid monomer. Theseamounts are not intended to be limiting. Binder materials comprisingcarboxylated nitrile rubber are preferred because they produce fabricshaving outstanding abrasion resistance and excellent strength. Suchterpolymers are well known in the art and are commercially available,for example, from Dow Reichhold Specialty Latex, LLC. of ResearchTriangle Park, N.C., under the trademark TYLAC® 68073. Usefulcarboxylated nitrile rubber terpolymers are also described, for example,in U.S. Pat. Nos. 6,127,469, 6,548,604 and 7,030,193, the disclosures ofwhich are incorporated herein by reference. Another preferred terpolymercomprises an acrylonitrile monomer, a butadiene monomer and N-methylolacrylamide (NMA). One example of this type of terpolymer is HYCAR®1572X64, commercially available from Emerald Performance Materials ofAkron, Ohio.

Other useful terpolymers of this type are described, for example, inU.S. Pat. No. 5,783,625 and Canadian patent CA 1190343, the disclosuresof which are incorporated herein by reference. A preferredacrylonitrile/butadiene/NMA terpolymer preferably comprises from about0.3 weight % to about 10 weight % of the NMA monomer, more preferablyfrom about 1 wt. % to about 10 wt. % and most preferably from about 2wt. % to about 4 wt. % of the NMA monomer. U.S. Pat. No. 5,783,625describes a useful range of self-crosslinking NMA monomer of between0.3% and 10%. Canadian patent CA1190343 provides rubber compositionsincluding (A) 10-90% by weight of a terpolymer consisting of aconjugated diolefin, an α, β-unsaturated nitrile and an α, β-unsaturatedcarboxylic ester, (B) 10-90% by weight of a sulfur-vulcanizable acrylicrubber and (C) 0-40% by weight of a copolymer consisting of a conjugateddiolefin and an α, β-unsaturated nitrile having a combined α,β-unsaturated nitrile content of 10-60% by weight. This rubbercomposition has excellent processability, oil resistance and heatresistance.

Optionally, the nitrile rubbers of the invention may be hydrogenated toimprove durability and environmental resistance. Particularly,hydrogenated nitrile rubbers (HNBR) have excellent mechanical,thermo-oxidative and chemical resistant properties and an excellentoperating temperature range. Hydrogenated nitrile rubbers are well knownin the art.

In another embodiment of the invention, the polymeric binder materialmay comprise a blend of a nitrile rubber and a fluoropolymer and/or afluorocarbon resin. It has been found that a polymeric binder materialcomprising a blend of a nitrile rubber component and one or morefluorine-containing components have a significantly improved V₅₀retention % after immersion in either salt water or gasoline, i.e.greater than or equal to 95% retention as illustrated in the inventiveexamples, compared to fabrics formed with neither nitrile rubber nor afluorine-containing material. As used herein, a “fluorine-containing”material includes fluoropolymers and fluorocarbon-containing materials(i.e. fluorocarbon resins). A “fluorocarbon resin” generally refers topolymers including fluorocarbon groups. When such blends are formed, noreaction takes place between the nitrile rubber polymer and thefluoropolymer/fluorocarbon resin. A copolymer is not formed, only aphysical blend. It has also been recognized that thefluoropolymer/fluorocarbon resin, which will normally have a lowermolecular weight than the nitrile rubber, tends to concentrate andorganize itself at the boundaries, such as at the outer fabric surfaces(i.e. the air-to-binder interface, i.e. the outside surface, and thefiber-to-binder interface, i.e. the inside surface). This distributionof the fluorocarbon resin at the surfaces increases the effectiveness ofthe fluorocarbon resin in regards to its enhancing the environmentalresistance (salt water, gasoline, etc.) of the composite. In thisembodiment, the type of nitrile rubber is not limited and may comprise,for example, XNBR, HNBR or non-hydrogenated nitrile rubber.

Fluorine-containing materials, particularly fluoropolymers andfluorocarbon resin materials, are commonly known for their excellentchemical resistance and moisture barrier properties. Usefulfluoropolymer and fluorocarbon resin materials herein includefluoropolymer homopolymers, fluoropolymer copolymers or blends thereofas are well known in the art and are described in, for example, U.S.Pat. Nos. 4,510,301, 4,544,721 and 5,139,878. Examples of usefulfluoropolymers include, but are not limited to, homopolymers andcopolymers of chlorotrifluoroethylene, ethylene-chlorotrifluoroethylenecopolymer, ethylene-tetrafluoroethylene copolymer, fluorinatedethylene-propylene copolymer, perfluoroalkoxyethylene,polychlorotrifluoroethylene, polytetrafluoroethylene, polyvinylfluoride, polyvinylidene fluoride, and copolymers and blends thereof.

Preferred fluoropolymers include homopolymers and copolymers ofpolychlorotrifluoroethylene. Particularly preferred are PCTFE(polychlorotrifluoroethylene homopolymer) materials sold under theACLON™ trademark and which are commercially available from HoneywellInternational Inc. of Morristown, N.J. The most preferred fluoropolymersor fluorocarbon resins include fluorocarbon-modified polymers,particularly fluoro-oligomers and fluoropolymers formed by grafting,condensing or reacting fluorocarbon side-chains onto or copolymerizingfluorocarbon side chain-containing monomers (such as perfluorooctanoicacrylate) into conventional polyethers (i.e. fluorocarbon-modifiedpolyethers), polyesters (i.e. fluorocarbon-modified polyesters),polyanions (i.e. fluorocarbon-modified polyanions) such as polyacrylicacid (i.e. fluorocarbon-modified polyacrylic acid) or polyacrylates(i.e. fluorocarbon-modified polyacrylates), and polyurethanes (i.e.fluorocarbon-modified polyurethanes). One particularly preferredfluorocarbon resin is NUVA® TTHU, a perfluoroalkyl acryliccopolymerizate commercially available from Clariant International, Ltd.of Switzerland. These fluorocarbon side chains or perfluoro compoundsare generally produced by a telomerization process and are referred toas C₈ fluorocarbons. For example, a fluoropolymer or fluorocarbon resinmay be derived from the telomerization of an unsaturatedfluoro-compound, forming a fluorotelomer, where said fluorotelomer isfurther modified to allow reaction with a polyether, polyester,polyanion, polyacrylic acid, polyacrylate or polyurethane, and where thefluorotelomer is then grafted onto a polyether, polyester, polyanion,polyacrylic acid, polyacrylate or polyurethane. Fluorocarbon resins mayalso be produced, for example, by the copolymerization of a fluorocarbonside chain-containing monomer with a conventional monomers, such as anoligomer formed by the copolymerization of butyl acrylate or ethylacrylate and perfluorooctanoic acrylate. Good representative examples ofthese fluorocarbon-containing polymers are NUVA® fluoropolymer products,commercially available from Clariant International, Ltd. of Switzerland.Other fluorocarbon resins, fluoro-oligomers and fluoropolymers havingperfluoro acid-based, perfluoro acrylate-based and perfluoroalcohol-based side chains are also most preferred. Fluoropolymers andfluorocarbon resins having fluorocarbon side chains of shorter lengths,such as C₆, C₄ or C₂, are also suitable, such as POLYFOX™fluorochemicals, commercially available from Omnova Solutions, Inc. ofFairlawn, Ohio. Generally, but not necessarily thefluorocarbon-containing component and nitrile rubber component are bothwet (i.e. in the molten or liquid state, dispersed or dissolved) whenthey are blended to facilitate their miscibility and blendability, andare applied to the fibers as a wet blend.

While fluoropolymers and fluorocarbon resins increase the environmentalbarrier properties, they tend to lack optimal processability andflexibility properties, as well as other physical properties generallyconsidered useful in ballistic resistant composites. These importantproperties are provided by the nitrile rubber component, and togetherthey produce a superior binder material.

In a blend, the proportion of the nitrile rubber component to thefluorine-containing component should be set to allow the physicalproperties of the blended matrix composition to be dominated by thephysical properties of the nitrile rubber component. At a minimum, thenitrile rubber component should be in excess of the fluorine-containingcomponent(s). The physical properties of the fluorine-containingcomponent(s) are of secondary importance. The fluorine-containingcomponent or components will be chosen due to their ability to repelwater and gasoline, as well as their ability to be compounded into astable or useful blended emulsion/dispersion with the nitrile rubbercomponent.

In the preferred embodiments of the invention, the fluorine-containingcomponent comprises from about 1% by weight to about 50% by weight ofthe nitrile rubber containing polymeric binder material. Morepreferably, the fluorine-containing component comprises from about 3% toabout 35% by weight of the nitrile rubber-containing polymeric bindermaterial, more preferably from about 5% to about 25% by weight, and morepreferably from about 5% to about 20% by weight of the nitrilerubber-containing polymeric binder material. The nitrile rubberdispersions used to produce the polymer composition preferably have asolids content of from about 30% to about 50%, although values outsidethis range are possible. The fluorocarbon resin dispersions used toproduce the polymer composition preferably have a solids content of fromabout 8% to about 30%, but values outside this range are also possible.A dry binder including a fluoropolymer/fluorocarbon resin mostpreferably includes a fluoropolymer/fluorocarbon resin solids content offrom about 8% to about 12%, solids-on-solids. For example, a blendincluding 85 wt. % of a nitrile rubber dispersion (at 40% solids) and 15wt. % of a fluorocarbon resin dispersion (at 25% solids), would include9.93% of dry fluorocarbon resin if dried to form a dry blend.

It has been found that a new polymer composition which comprises a blendof at least one fluorine-containing material and at least one nitrilerubber terpolymer is particularly useful herein. When such blends areformed no reaction takes place between the nitrile rubber polymer andthe fluoropolymer/fluorocarbon resin and a copolymer is not formed. Itis only a physical blend. The nitrile rubber terpolymer is a copolymermade from three different monomers: an acrylonitrile monomer component,a diene monomer component and a third monomer component. The dienemonomer component preferably comprises butadiene. The third monomercomponent is preferably a self-crosslinking monomer and preferablycomprises a carboxylic acid or an ester of an unsaturated carboxylicacid. Useful self-crosslinking monomers are disclosed, for example, inU.S. Pat. No. 5,783,625, the disclosure of which is incorporated hereinby reference. More particularly, useful examples for the third monomercomponent non-exclusively include N-methylolacrylamide,N-methylolmethacrylamide, N,N′-dimethylolacrylamide,N,N′-dimethylolmethacrylamide, acrylamide, methacrylamide,N-methoxymethylacrylamide, N-methoxymethylmethacrylamide,N-ethoxymethylacrylamide N-ethoxymethylmethacrylamide,N-butoxymethylacrylamide, N-butoxymethylmethacrylamide andN,N′-methylene-bisacrylamide, N-(anilinophenyl)acrylamide,N-(anilinophenyl)methacrylamide, N-(anilinophenyl)cinnamamide,N-(anilinophenyl)crotonamide, N-(anilinophenyl)amino2-hydroxypropylallyl ether, N-(anilinophenyl)amino-2-hydroxypropyl methallyl ether,5-N-(4-anilinophenyl)amino-2-hydroxypentyl acrylate and5-N-(4-anilinophenyl)amino-2-hydroxypentyl methacrylate. Also useful aremethyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate,2-ethylhexyl methacrylate, trifluoroethyl acrylate, trifluoroethylmethacrylate, tetrafluoropropyl acrylate, tetrafluoropropylmethacrylate, ethyl itaconate, butyl fumarate, butyl maleate,methoxymethyl acrylate, methoxymethyl methacrylate, ethoxyethylacrylate, ethoxyethyl methacrylate, methoxyethoxyethyl acrylate andmethoxyethoxyethyl methacrylate; cyanoalkyl esters of acrylic acid andmethacrylic acid such as cyanomethyl acrylate, cyanomethyl methacrylate,2-cyanoethyl acrylate, 2-cyanoethyl methacrylate, 1-cyanopropylacrylate, 1-cyanopropyl methacrylate, 2-ethyl-6-cyanohexyl acrylate,2-ethyl-6-cyanohexyl methacrylate, 3-cyanopropyl acrylate and3-cyanopropyl methacrylate; fluoroalkyl vinyl ethers such as fluoroethylvinyl ether; and vinylpyridine.

The nitrile rubber terpolymer component of this unique nitrilerubber/fluoropolymer (fluorocarbon) polymer composition preferablyincludes an acrylonitrile content of from about 15 wt. % to about 50 wt.%, more preferably from about 15 wt. % to about 40 wt. % and mostpreferably from about 15 wt. % to about 30 wt. %. The nitrile rubberterpolymer component of this new polymer preferably includes a butadienecontent of from about 40 wt. % to about 84.9 wt. %, more preferably fromabout 55 wt. % to about 84.5 wt. % and most preferably from about 66 wt.% to about 83 wt. %. The nitrile rubber terpolymer component of this newpolymer preferably includes from about 0.1 wt. % to about 10 wt. %, morepreferably from about 0.5 wt. % to about 5 wt. % and most preferablyfrom about 2 wt. % to about 4 wt. % of said third monomer component.

Most preferably the nitrile rubber terpolymer comprises a terpolymerformed from an acrylonitrile monomer component, a butadiene monomercomponent and either N-methylol acrylamide or a carboxylic acid monomercomponent. A most preferred nitrile rubber terpolymer comprisescarboxylated nitrile rubber. The nitrile rubber terpolymer component ofthis new polymer preferably comprises from about 60 wt. % to about 99wt. % of said polymer composition, more preferably from about 75 wt. %to about 97 wt. % and most preferably from about 85 wt. % to about 95wt. %. Accordingly, the fluorine-containing component of this newpolymer preferably comprises from about 1 wt. % to about 40 wt. % ofsaid polymer composition, more preferably from about 3 wt. % to about 25wt. % and most preferably from about 5 wt. % to about 15 wt. %,solids-on-solids. Useful fluorine-containing materials are describedabove.

The polymeric binder materials preferably further comprise at least onesurfactant. It has been unexpectedly found that the addition of asurfactant to a binder of the invention achieves improved uniformity ofthe binder coating on the individual fibers. It has also been found thatthe addition of a surfactant increases the stability of a blendeddispersion and promotes the uniformity of the distribution of afluorocarbon resin, if present, at the air-to-binder and fiber-to-binderinterfaces of a nitrile rubber/fluorocarbon resin blend. The surfactantmay be included whether the fluoropolymer is present or not. Suitablesurfactants non-exclusively include anionic, cationic, amphoteric andnon-ionic surfactants. Generally, non-ionic surfactants are preferredbecause they have the most limited solubility in water and do not formsalts with anionic surfactants. Further, the polymeric binder materialsare very sensitive to anionic and cationic surfactants because the highcharge density may lead to coagulation of the dispersions. Non-ionicsurfactants typically do not interfere with the nature of the dispersedpolymers (micelles containing solids), or exhibit minimal interference.Preferred non-ionic surfactants include non-ionic surfactants based onfatty acids and fatty alcohols, particularly those havinghydrophile-lipophile balance (HLB) values of 7 to 10. A particularlypreferred surfactant is a non-ionicpolyethylene-glycol-trimethylnonyl-ether, such as TERGITOL® TMN-3surfactant commercially available from Dow Chemical Company of Midland,Mich. TERGITOL® TMN-3 is preferred because it provides a low surfacetension at a low concentration. Low surface tension is desired to makesure the dispersion spreads well and covers each individual fiber.TERGITOL® TMN-3 has an HLB value of approximately 8 and exhibits carbonchain branching that helps reducing surface tension. Also useful arenon-ionic fluorosurfactants, such as Fluowet® fluorosurfactants fromClariant GmbH Corporation of Germany, particularly Fluowet® OTN.However, fluorosurfactants may not be acceptable due to environmentalconcerns. Also useful are silicone surfactants in combination withethoxylated castor oils that are partially end-capped with oleic acid.

In the preferred embodiment of the invention, a surfactant is presentand comprises from about 0.01% to about 10% by weight of the polymericbinder material, more preferably from about 0.05% to about 5% by weight,and most preferably from about 0.1% to about 2.5% by weight of thepolymeric binder material. The polymeric composition may also includefillers such as carbon black or silica, may be extended with oils, ormay be vulcanized by sulfur, peroxide, metal oxide or radiation curesystems as is well known in the art.

To produce a fabric article having sufficient ballistic resistanceproperties, the proportion of fibers forming the fabric preferablycomprises from about 50% to about 98% by weight of the fibers plus thepolymeric binder material, more preferably from about 70% to about 95%,and most preferably from about 78% to about 90% by weight of the fibersplus the polymeric binder material. Thus, the polymeric binder materialpreferably comprises from about 2% to about 50% by weight of the fabric,more preferably from about 5% to about 30% and most preferably fromabout 10% to about 22% by weight of the fabric, wherein 16% is mostpreferred.

The application of the polymeric binder material is conducted prior toconsolidating non-woven fiber plies, and the binder coating is to beapplied on top of any pre-existing fiber finish, such as a spin finishor may be applied after partial or complete removal of any pre-existingfiber finish. The fibers of the invention may be coated on, impregnatedwith, embedded in, or otherwise applied with a polymeric binder materialby applying the composition to the fibers, followed by consolidating thecoated fibers to form a composite. The binder material may first beapplied onto a plurality of fibers followed by forming at least onefiber ply from said fibers, where the individual fibers are coatedeither sequentially or concurrently. Alternately, at least one fiber plymay be formed first followed by applying the polymeric binder materialonto said at least one fiber ply.

For the purposes of the present invention, the term “coated” is notintended to limit the method by which the polymeric binder material isapplied onto the fiber surfaces and any appropriate method of applyingthe polymeric composition onto the fiber surfaces may be utilized. Forexample, the polymeric binder material may be applied in solution formby spraying or roll coating a solution of the composition onto fibersurfaces, wherein a portion of the solution comprises the desiredpolymer or polymers and a portion of the solution comprises a solventcapable of dissolving or dispersing the polymer or polymers, followed bydrying. Another method is to apply a neat polymer of the coatingmaterial to fibers either as a liquid, a sticky solid or particles insuspension or as a fluidized bed. Alternatively, the coating may beapplied as a solution, emulsion or dispersion in a suitable solventwhich does not adversely affect the properties of the fiber at thetemperature of application. For example, the fiber can be transportedthrough a solution of the polymeric binder material to substantiallycoat the fiber and then dried to form a coated fiber. The resultingcoated fiber is then arranged into the desired configuration. In anothercoating technique, fiber plies or woven fabrics may first be arranged,followed by dipping the plies or fabrics into a bath of a solutioncontaining the polymeric binder material dissolved in a suitablesolvent, such that each individual fiber is at least partially coatedwith the polymeric binder material, and then dried through evaporationor volatilization of the solvent. The dipping procedure may be repeatedseveral times as required to place a desired amount of polymeric bindermaterial coating onto the fibers, preferably encapsulating each of theindividual fibers or covering all or substantially all of the fibersurface area with the polymeric binder material.

While any liquid capable of dissolving or dispersing a polymer may beused, preferred groups of solvents include water, paraffin oils andaromatic solvents or hydrocarbon solvents, with illustrative specificsolvents including paraffin oil, xylene, toluene, octane, cyclohexane,methyl ethyl ketone (MEK) and acetone. The techniques used to dissolveor disperse the coating polymers in the solvents will be thoseconventionally used for the coating of similar materials on a variety ofsubstrates.

Other techniques for applying the coating to the fibers may be used,including coating of the high modulus precursor (gel fiber) before thefibers are subjected to a high temperature stretching operation, eitherbefore or after removal of the solvent from the fiber (if using agel-spinning fiber forming technique). The fiber may then be stretchedat elevated temperatures to produce the coated fibers. The gel fiber maybe passed through a solution of the appropriate coating polymer underconditions to attain the desired coating. Crystallization of the highmolecular weight polymer in the gel fiber may or may not have takenplace before the fiber passes into the solution. Alternatively, thefibers may be extruded into a fluidized bed of an appropriate polymericpowder. Furthermore, if a stretching operation or other manipulativeprocess, e.g. solvent exchanging, drying or the like is conducted, thecoating may be applied to a precursor material of the final fibers. Inthe most preferred embodiment of the invention, the fibers of theinvention are first coated with the polymeric binder material, followedby arranging a plurality of fibers into either a woven or non-wovenfabric. Such techniques are well known in the art.

As is well known in the art, consolidation is done by positioning theindividual fiber plies on one another under conditions of sufficientheat and pressure to cause the plies to combine into a unitary fabric.Consolidation may be done at temperatures ranging from about 50° C. toabout 175° C., preferably from about 105° C. to about 175° C., and atpressures ranging from about 5 psig (0.034 MPa) to about 2500 psig (17MPa), for from about 0.01 seconds to about 24 hours, preferably fromabout 0.02 seconds to about 2 hours. When heating, it is possible thatthe polymeric binder material can be caused to stick or flow withoutcompletely melting. However, generally, if the polymeric binder materialis caused to melt, relatively little pressure is required to form thecomposite, while if the polymeric binder material is only heated to asticking point, more pressure is typically required. Consolidation mayalso be achieved by a wet lamination of the first fibrous web to thesecond fibrous web without requiring heat and/or pressure. As isconventionally known in the art, consolidation may be conducted in acalender set, a flat-bed laminator, a press or in an autoclave.

Alternately, consolidation may be achieved by molding under heat andpressure in a suitable molding apparatus. Generally, molding isconducted at a pressure of from about 50 psi (344.7 kPa) to about 5000psi (34470 kPa), more preferably about 100 psi (689.5 kPa) to about 1500psi (10340 kPa), most preferably from about 150 psi (1034 kPa) to about1000 psi (6895 kPa). Molding may alternately be conducted at higherpressures of from about 500 psi (3447 kPa) to about 5000 psi, morepreferably from about 750 psi (5171 kPa) to about 5000 psi and morepreferably from about 1000 psi to about 5000 psi. The molding step maytake from about 4 seconds to about 45 minutes. Preferred moldingtemperatures range from about 200° F. (˜93° C.) to about 350° F. (˜177°C.), more preferably at a temperature from about 200° F. to about 300°F. (˜149° C.) and most preferably at a temperature from about 200° F. toabout 280° F. (˜121° C.). The pressure under which the fabrics of theinvention are molded has a direct effect on the stiffness or flexibilityof the resulting molded product. Particularly, the higher the pressureat which the fabrics are molded, the higher the stiffness, andvice-versa. In addition to the molding pressure, the quantity, thicknessand composition of the fabric plies and polymeric binder material typealso directly affects the stiffness of the articles formed from theinventive fabrics.

While each of the molding and consolidation techniques described hereinare similar, each process is different. Particularly, molding is a batchprocess and consolidation is a continuous process. Further, moldingtypically involves the use of a mold, such as a shaped mold or amatch-die mold when forming a flat panel, and does not necessarilyresult in a planar product. Normally consolidation is done in a flat-bedlaminator, a calendar nip set or as a wet lamination to produce softbody armor fabrics. Molding is typically reserved for the manufacture ofhard armor, e.g. rigid plates. In the context of the present invention,consolidation techniques and the formation of soft body armor arepreferred.

In either process, suitable temperatures, pressures and times aregenerally dependent on the type of polymeric binder coating materials,polymeric binder content (of the combined coatings), process used andfiber type. The fabrics formed herein may optionally be calendered underheat and pressure to smooth or polish their surfaces. Calenderingmethods are well known in the art.

The thickness of the individual fabrics will correspond to the thicknessof the individual fibers. A preferred woven fabric will have a preferredthickness of from about 25 μm to about 500 μm per layer, more preferablyfrom about 50 μm to about 385 μm and most preferably from about 75 μm toabout 255 μm per layer. A preferred non-woven fabric, i.e. a non-woven,single-layer, consolidated network, will have a preferred thickness offrom about 12 μm to about 500 μm, more preferably from about 50 μm toabout 385 μm and most preferably from about 75 μm to about 255 μm,wherein a single-layer, consolidated network typically includes twoconsolidated plies (i.e. two unitapes), with the exception of theCOMPARATIVE A composite utilized in the comparative examples, where asingle layer of the composite includes four plies. While suchthicknesses are preferred, it is to be understood that other thicknessesmay be produced to satisfy a particular need and yet fall within thescope of the present invention.

The fabrics of the invention will have a preferred areal density of fromabout 50 grams/m² (gsm) (0.01 lb/ft² (psf)) to about 1000 gsm (0.2 psf).More preferable areal densities for the fabrics of this invention willrange from about 70 gsm (0.014 psf) to about 500 gsm (0.1 psf). The mostpreferred areal density for fabrics of this invention will range fromabout 100 gsm (0.02 psf) to about 250 gsm (0.05 psf). The articles ofthe invention, which consist of multiple individual layers of fabricstacked one upon the other, will further have a preferred areal densityof from about 1000 gsm (0.2 psf) to about 40,000 gsm (8.0 psf), morepreferably from about 2000 gsm (0.40 psf) to about 30,000 gsm (6.0 psf),more preferably from about 3000 gsm (0.60 psf) to about 20,000 gsm (4.0psf), and most preferably from about 3750 gsm (0.75 psf) to about 10,000gsm (2.0 psf).

The structures of the invention may be used in various applications toform a variety of different ballistic resistant articles using wellknown techniques. For example, suitable techniques for forming ballisticresistant articles are described in, for example, U.S. Pat. Nos.4,623,574, 4,650,710, 4,748,064, 5,552,208, 5,587,230, 6,642,159,6,841,492 and 6,846,758. The structures are particularly useful for theformation of flexible, soft armor articles, including garments such asvests, pants, hats, or other articles of clothing, and covers orblankets, used by military personnel to defeat a number of ballisticthreats, such as 9 mm full metal jacket (FMJ) bullets and a variety offragments generated due to explosion of hand-grenades, artillery shells,Improvised Explosive Devices (IED) and other such devises encountered ina military and peace keeping missions.

As used herein, “soft” or “flexible” armor is armor that does not retainits shape when subjected to a significant amount of stress. Thestructures are also useful for the formation of rigid, hard armorarticles. By “hard” armor is meant an article, such as helmets, panelsfor military vehicles, or protective shields, which have sufficientmechanical strength so that it maintains structural rigidity whensubjected to a significant amount of stress and is capable of beingfreestanding without collapsing. The structures can be cut into aplurality of discrete sheets and stacked for formation into an articleor they can be formed into a precursor which is subsequently used toform an article. Such techniques are well known in the art.

Garments of the invention may be formed through methods conventionallyknown in the art. Preferably, a garment may be formed by adjoining theballistic resistant articles of the invention with an article ofclothing. For example, a vest may comprise a generic fabric vest that isadjoined with the ballistic resistant structures of the invention,whereby the inventive structures are inserted into strategically placedpockets. This allows for the maximization of ballistic protection, whileminimizing the weight of the vest. As used herein, the terms “adjoining”or “adjoined” are intended to include attaching, such as by sewing oradhering and the like, as well as un-attached coupling or juxtapositionwith another fabric, such that the ballistic resistant articles mayoptionally be easily removable from the vest or other article ofclothing. Articles used in forming flexible structures like flexiblesheets, vests and other garments are preferably formed from using a lowtensile modulus binder material. Hard articles like helmets and armorare preferably, but not exclusively, formed using a high tensile modulusbinder material.

The ballistic resistance properties are determined using standardtesting procedures that are well known in the art. Particularly, theprotective power or penetration resistance of a structure is normallyexpressed by citing the impacting velocity at which 50% of theprojectiles penetrate the composite while 50% are stopped by the shield,also known as the V₅₀ value. As used herein, the “penetrationresistance” of an article is the resistance to penetration by adesignated threat, such as physical objects including bullets,fragments, shrapnel and the like, and non-physical objects, such as ablast from explosion. For composites of equal areal density, which isthe weight of the composite divided by its area, the higher the V₅₀, thebetter the ballistic resistance of the composite. The ballisticresistant properties of the articles of the invention will varydepending on many factors, particularly the type of fibers used tomanufacture the fabrics, the percent by weight of the fibers in thecomposite, the suitability of the physical properties of the resinmatrix, the number of layers of fabric making up the composite and thetotal areal density of the composite. However, the use of a polymericbinder material that is resistant to dissolution or penetration by seawater, and resistant to dissolution or penetration by one or moreorganic solvents, does not negatively affect the ballistic properties ofthe articles of the invention. The fabrics of the invention also haveexcellent durability as indicated by good peel strength and flexibilityof the fabrics, as illustrated in the examples.

The following examples serve to illustrate the invention:

EXAMPLES

Various fabric samples were tested as exemplified below. Table 1describes the fabric samples tested in the Examples and ComparativeExamples. For Sample A, the binder is an unmodified, water-basedpolyurethane polymer. For Sample B, the binder is a rosin ester-modifieddispersion of a styrene-isoprene-styrene (SIS) block copolymer soldunder the trademark PRINLIN® and commercially available from HenkelTechnologies, based in Düsseldorf, Germany. For Sample C, the binder isa fluorocarbon-modified, water-based acrylic polymer (84.5 wt. % acryliccopolymer sold as HYCAR® 26-1199, commercially available from Noveon,Inc. of Cleveland, Ohio; 15 wt. % NUVA® NT X490 fluorocarbon resin,commercially available from Clariant International, Ltd. of Switzerland;and 0.5% Dow TERGITOL® TMN-3 non-ionic surfactant commercially availablefrom Dow Chemical Company of Midland, Mich.). For Sample D, the binderis a fluorocarbon-modified polyurethane polymer (84.5 wt. % polyurethanepolymer sold as SANCURE® 20025, from Noveon, Inc.; 15 wt. % NUVA® NTX490 fluorocarbon resin; and 0.5% Dow TERGITOL® TMN-3 non-ionicsurfactant). For Sample E, the binder is a fluoropolymer/nitrile rubberblend of the invention (84.5 wt. % nitrile rubber polymer sold asTYLAC®68073 from Dow Reichhold of N.C.; 15 wt. % NUVA® TTHU fluorocarbonresin; and 0.5% Dow TERGITOL® TMN-3 non-ionic surfactant). Fabricsamples F and G are woven fabrics with no binder.

Fabric samples A and C-E were non-woven, aramid-based fabrics with atwo-ply (two unitape), 0°/9° construction. The fabrics are manufacturedfrom 1000-denier TWARON® type 2000 aramid fibers having a fiber arealdensity (FAD) of 45 gsm, and had a fiber content of 85%. Fabric sample Bwas similar but had a four-ply 0°/90/0°/90 construction and a layer of0.25-mil thick LDPE film laminated to both outside plies. Each ply has afiber content of 85%, but the final construction, including the LDPEfilm, has a fiber content of approximately 80%. The Fiber Areal Density(FAD) of each ply (unitape) was 45 gsm. The non-woven fabrics wereconsolidated into integrated fabrics. Fabric sample F was a woven,aramid based fabric manufactured from 500-denier, TWARON® Type 2000aramid fibers with a pick count of 28×28 and a fiber content of 100%.Fabric sample G was a woven, aramid based fabric manufactured from600-denier, KEVLAR® KM2 aramid fibers with a pick count of 29×29 and afiber content of 100%. The fabric samples are summarized in Table 1.

TABLE 1 SAMPLE CONSTRUCTION Fiber Type Resin % Fiber A 2-ply, 0°/90°1000-denier Polyurethane 85% Non-Woven Aramid B 4-ply, 1000-denier Rosinester- 78% 0°/90°/0°/90° Aramid modified Non-Woven with S-I-S LDPE filmover- Rubber laminate C 2-ply, 0°/90° 1000-denier Modified 85% Non-WovenAramid Acrylic D 2-ply, 0°/90° 1000-denier Modified 85% Non-Woven AramidPolyurethane E 2-ply, 0°/90° 1000-denier Modified 85% Non-Woven AramidNitrile Rubber F 28 × 28 Woven 500-denier None 100% TWARON ® Type 2000Aramid G 29 × 29 Woven 600-denier None 100% KEVLAR ® KM2 Aramid

Articles of ballistic resistant armor can be designed and constructed soas to achieve a desired V₅₀ by adding or subtracting individual layersof ballistic resistant fabric. For the purpose of these experiments, theconstruction of the articles was standardized by stacking a sufficientnumber of fabric layers such that the Total Areal Density (TAD) (arealdensity of fabrics including the fibers and the polymeric bindermaterial) of the article was 1.00±0.02 psf. Depending on the TAD of theindividual fabric layers, the count of layers required to maintain thearticle's targeted TAD between 0.98 psf and 1.02 psf ranged between 44and 47 for Samples A, C, D and E. For Sample B, a total of 21 layers areneeded to give a resulting TAD of 1.00 PSF. For Sample F, the wovenaramid Style #275580, a total of 39 layers are needed to give aresulting TAD of 1.00 PSF. For Sample G, the woven aramid Style #751, atotal of 32 layers are needed to give a resulting TAD of 1.00 PSF. Eachof these stacks of fabric was then placed into a nylon fabric rip-stopcarrier, which was then stitched closed. At this point, the assembly wasconsidered to be the ballistic article sample upon which testing wouldbe done.

Including the polymeric binder material, the TAD of each single unitapeply of the non-woven fabrics ranged from 52.5 gsm to 54.0 gsm. The TADof each fabric layer for Samples A, C, D and E (equal to twice the TADof each single-ply for a two-ply fabric) ranged from 105 gsm to 108 gsm.For Sample B, the TAD for a fabric layer would range from 218 gsm to 228gsm. Each layer of fabric was a nominal 15″×15″ square. These fabriclayers were then assembled into an article, as described above.

The V₅₀ ballistic resistance of several different fabric test packs wasevaluated after submersion in salt water and after submersion ingasoline, respectively. Inventive Examples 5 and 12 show the performanceof inventive fabric Sample E following the salt water and gasolinesubmersion. Comparative Examples 1-4, 6-11 and 13-14 show theperformance of comparative fabric Samples A-D and F-G following the saltwater and gasoline submersion. Results for said testing are shown inTables 2 and 3. Additional testing was also conducted without gasolineor water submersion, and the results are provided in Tables 4-7. Table 4outlines the ballistic testing results of said fabrics against 17 grainFSP fragments (fragment confirming: MIL-P-46593A) following thestandardized testing conditions of MIL-STD-662F. Table 5 outlines theballistic testing results of said fabrics against a 9 mm, 124 grain, FMJ(full metal jacket) bullet, following the standardized testingconditions of MIL-STD-662F. Table 6 illustrates the flexibility of eachsample according to the circular bend test method of ASTM D4032. Table 7illustrates the peel strength/interlayer bond strength of each non-wovensample (Samples A-E) according to the test method of ASTM D1876-01.

The procedures for the ballistic evaluation after environmental exposureto salt water and gasoline, and for the preparation of the test samplesare outlined as follows:

A. Procedure for the Ballistic Evaluation of a Polymeric Binder Materialafter Environmental Exposure

Hardware:

-   -   1. Salt water immersion tray - plastic, flat-bottom open-top        containers, 18″ wide by 24″ long by 6″ deep.    -   2. Drying frame and clips.    -   3. Gasoline immersion chamber—stainless steel enclosure,        approximately 24-inches wide by 24-inches deep by 36-inches        high. The enclosure includes a front access door, a top access        lid and several mounting bars bridging the left and right walls,        one-inch from the top of the walls.    -   4. Gasoline immersion transport carrier.    -   5. Weighing scale.    -   6. Indelible marker pen.    -   7. Timer.    -   8. Ballistic mounting frame.    -   9. Ballistics range capable of firing and determining the        velocity of 16-grain RCC fragments.

Materials:

-   -   1. 15-inch by 15-inch squares of the non-woven fabrics to be        evaluated.    -   2. 16-inch by 16-inch nylon “rip-stop” carriers.    -   3. De-ionized water.    -   4. Sea Salt (or mixture of Sodium Chloride and Magnesium        Chloride).    -   5. 5 Gallons of U.S. regular-grade (87-octane, unleaded)        gasoline.    -   6. 16-grain RCC fragments.

B. Procedure for Preparing the Test Packs

-   -   1. Ten 15-inch by 15-inch square samples of each fabric were        weighed to determine a Total Areal Density (TAD) of a fabric        sample.    -   2. The number of these samples required to equal a sample TAD of        1.00 lb/ft² (PSF)±0.02 PSF was determined. This number was        defined as the “Layer Count”.    -   3. Twelve stacks of the 15-inch by 15-inch squares were prepared        for each fabric. The number of 2-ply layers of fabric (or 4-ply        for Sample B fabric) in each stack was the same as the “Layer        Count”, and a consistent orientation of the fibers in each        sample was maintained (i.e. the fibers of the top ply in each        sample were all pointed in the same direction).    -   4. When all twelve stacks had the required “Layer Count”, each        stack was weighed to determine whether an adjustment in the        “Layer Count” was needed to achieve a nominal 1.00 PSF test pack        (shoot pack). Any discrepancy in the number of layers between        stacks was adjusted to have twelve equivalent stacks of 1.00 PSF        fabric samples.    -   5. Once twelve equivalent stacks of 1.00 lb. fabric layers were        formed, each was inserted into a 16-inch by 16-inch nylon        “rip-stop” carrier. The open end of the carrier was sewn to        contain the test pack. Each carrier/test pack was corner        stitched.    -   6. Using an indelible marker, all of the particulars of each        test pack were recorded, including a unique identifier for each        test pack on to the surface of the carrier. The test packs were        re-weighed including the nylon carrier.    -   7. The twelve test packs were separated into four groups of        three test packs: one group was used as the dry control for salt        water immersion testing; another group was used for salt water        immersion testing; another group was used as the dry control for        gasoline immersion testing; and the final group was used for        gasoline immersion testing.

C. 24-Hour Salt Water Immersion

-   -   1. Two full 500-gram containers of Morton Sea Salt were poured        into an empty and clean salt water immersion tray. This salt was        covered with 7 gallons of clear-running tap water. The tray was        filled to approximately 3-inches of its 6-inch depth and stirred        with a spatula until all of the salt dissolved. Instead of        Morton Sea Salt a solution of 3.0% Sodium Chloride and 0.5%        Magnesium Chloride in tap water may be used.    -   2. One of the samples from the group designated for salt water        immersion testing was selected and its dry weight was verified        to match the weight that was previously recorded.    -   3. The first of the salt water immersion test samples was        completely submerged into the salt water solution. At one hour        intervals, one more test pack was submerged into the salt water        solution.    -   4. Once the first test pack was submerged in the salt water        solution for 24 hours, the sample was ready for ballistic        testing.

D. Ballistic Testing for Salt Water Immersion

-   -   1. The test pack was removed from the salt water solution, hung        by one corner from the drying frame and allowed to drip-dry for        15 minutes.    -   2. The drip-dried sample was transported to the ballistics range        and weighed to record its wet weight.    -   3. The sample was inserted into the ballistic mounting frame and        this assembly was placed into the firing range.    -   4. A series of 16-grain RCC fragments were shot into the sample        according to the MIL-STD-662E testing method. The velocity of        the projectiles was adjusted to achieve a mixture of complete        penetrations of the sample and partial penetrations of the        sample. The velocity of each shot was measured and a V₅₀ for the        sample was determined using accepted statistical analysis tools.    -   5. Thereafter, one of the samples from the dry control group was        tested according to steps 3 and 4 for comparison.    -   6. The above steps were continued for all the designated salt        water immersion testing samples and dry control samples and a        V₅₀ was determined for each.

E. 4-Hour Gasoline Immersion

-   -   1. Five gallons of U.S. regular grade (87-octane, unleaded)        gasoline were poured into the gasoline immersion chamber.    -   2. One of the samples from the group designated for gasoline        immersion testing was selected and its dry weight was verified        to match the weight that was previously recorded.    -   3. The first of the gasoline immersion test samples was        completely submerged into the gasoline. At one hour intervals,        one more test pack was submerged into the gasoline.    -   4. Once the first test pack was submerged in the Gasoline        Immersion Chamber for 4 hours, the first sample was ready for        ballistic testing.

F. Ballistic Testing for Gasoline Immersion

-   -   1. After 4 hours, the first sample was lifted out of the        gasoline and clipped to one of the mounting bars across the top        of the chamber. The sample was allowed to drip-dry for 15        minutes.    -   2. After the 15 minute drip-dry, the sample was removed from the        mounting bar and placed into the gasoline immersion transport        carrier and the lid closed.    -   3. The carrier was then transported to the ballistics        laboratory, and the sample was weighed to record its wet weight.    -   4. The sample was inserted into the ballistic mounting frame and        this assembly was placed into the firing range.    -   5. A series of 16-grain RCC fragments were shot into the sample        according to the MIL-STD-662E testing method. The velocity of        the projectiles was adjusted to achieve a mixture of complete        penetrations of the sample and partial penetrations of the        sample. The velocity of each shot was measured and a V₅₀ for the        sample was determined using accepted statistical analysis tools.    -   6. Thereafter, one of the samples from the dry control group was        tested according to steps 3 and 4 for comparison.    -   7. The above steps were continued for all the designated        gasoline immersion testing samples and dry control samples and a        V₅₀ was determined for each.

G. Results

TABLE 2 16 GRAIN RCC SALT WATER IMMERSION TESTING All Samples V₅₀ at1.00 PSF (ft/sec) V₅₀ Ex. Sample Test #1 #2 #3 Average Retention 1 A Dry2091 2085 2137 2104 Wet 1881 1851 1863 1865 89% 2 B Dry 2085 2095 20912090 Wet 1625 1639 1683 1649 79% 3 C Dry 2012 2083 2092 2062 Wet 20102043 2034 2029 98% 4 D Dry 2079 2045 2164 2096 Wet 2089 2024 2146 2086100%  5 E Dry 2171 2110 2089 2123 Wet 2091 2102 2090 2094 99% 6 F Dry NRNR NR NR Wet NR NR NR NR Good* 7 G Dry 1989 2034 2027 2017 Wet 2042 20472079 2056 102%  *Estimate.

This table shows the excellent performance of Sample E versus the16grain RCC fragment, both dry and after a 24 hour salt water immersion.

TABLE 3 16 grain RCC Gasoline Immersion Testing All Samples at V₅₀ 1.00PSF (ft/sec) V₅₀ Ex. Product Test #1 #2 #3 Average Retention 8 A DryHistorical Average 2009 Wet Limited Testing Low <90% 9 B Dry HistoricalAverage 2032 Wet Limited Testing Low <75% 10 C Dry 2133 2082 2031 2082Wet 2019 2061 2087 2056 99% 11 D Dry 1988 2155 2080 2074 Wet 2025 19641875 1955 94% 12 E Dry 2171 2110 2089 2123 Wet 2043 2002 1990 2012 95%13 F Dry — — — — Wet — — — — **98% 14 G Dry 1989 2034 2027 2017 Wet — —— — **98% **Estimates.

This table shows the excellent performance of Sample E versus the16grain RCC fragment, both dry and after a 4 hour gasoline immersion.

TABLE 4 17 grain FSP Fragment Testing All Samples at 1.00 PSF V₅₀(ft/sec) Product #1 #2 #3 #4 #5 Average A 1899 1905 1824 1901 1859 1878B 1802 1874 1840 1887 — 1851 C 1859 1912 1911 1952 1922 1911 D 1948 19271920 1953 1922 1934 E 1971 1989 2001 1974 1983 1984 F 2013 1996 20381975 1967 1998 G 1900 1847 1933 1912 1923 1903

This table shows the excellent Fragment performance of Sample E relativeto similar products and to woven aramid fabrics

TABLE 5 9 mm Testing All Samples at 1.00 PSF V₅₀ (ft/sec) Product #1 #2#3 #4 Average A 1688 1716 1741 — 1715 B 1755 1729 1685 — 1723 C 16691689 1690 1671 1680 D 1710 1681 1699 1740 1708 E 1704 1691 1724 17221710 F 1548 1639 1518 1528 1558 G 1575 1530 1579 1525 1552

This table shows the excellent bullet performance of Sample E relativeto similar products and woven aramid fabrics.

TABLE 6 Circular Bend Flexibility Single Layers Test Product #1 #2 #3Avg. force (Newtons) A 8.4 8.7 9.2 8.8 B 8.2 8.6 9.4 8.7 C 7.0 7.4 6.87.1 D 7.9 8.1 8.1 8.0 E 6.7 6.4 6.6 6.6 F 3.7 3.3 3.4 3.5 G 8.7 10.1 9.09.3

This table shows the high flexibility of Sample E when compared tosimilar non-woven products. Testing conducted according to the ASTMD4032 Circular Bend testing method.

TABLE 7 1″ Peel Strength Test Data in PLI of Width Samples at 1.00 PSFProduct #1 #2 #3 Averages Product Avg Load Avg Load Avg Load Load PeaksSpikes A 0.557 0.528 0.501 0.529 0.6441 122% B Historical Average of 2-3Bond 0.267 — — C 1.297 0.803 0.557 0.886 1.0021 113% D 1.032 1.067 1.5581.219 1.3853 114% E 2.031 1.863 2.13  2.008 2.132  106% F N/A N/A N/AN/A N/A N/A G N/A N/A N/A N/A N/A N/A

This table shows the high level and the consistency of interlayer bondstrength of the Sample E. This test does not apply to woven aramidfabrics.

While the present invention has been particularly shown and describedwith reference to preferred embodiments, it will be readily appreciatedby those of ordinary skill in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe invention. It is intended that the claims be interpreted to coverthe disclosed embodiment, those alternatives which have been discussedabove and all equivalents thereto.

1. A non-woven, ballistic resistant fabric comprising a plurality offibers arranged in an array, said fibers being united and forming afabric, said fibers having a tenacity of about 7 g/denier or more and atensile modulus of about 150 g/denier or more; and said fibers having apolymeric binder material thereon which comprises a nitrile rubberpolymer, said binder being resistant to dissolution, penetration and/ortranspiration by water and resistant to dissolution, penetration and/ortranspiration by one or more organic solvents, wherein the nitrilerubber polymer has an acrylonitrile content of from about 15 wt % toabout 50 wt % and which polymeric binder material comprises from about2% to about 50% by weight of the fabric.
 2. The ballistic resistantfabric of claim 1 wherein said nitrile rubber polymer is uncured.
 3. Theballistic resistant fabric of claim 1 wherein said polymeric bindermaterial has an acrylonitrile content of from about 15 wt. % to about 30wt. %.
 4. The ballistic resistant fabric of claim 1 wherein said nitrilerubber polymer comprises a nitrile rubber terpolymer.
 5. The ballisticresistant fabric of claim 1 wherein said nitrile rubber polymercomprises a terpolymer formed from an acrylonitrile monomer, a butadienerubber monomer and N-methylol acrylamide.
 6. The ballistic resistantfabric of claim 1 wherein said nitrile rubber polymer comprises acarboxylated nitrile rubber terpolymer.
 7. The ballistic resistantfabric of claim 1 wherein said nitrile rubber polymer comprises ahydrogenated nitrile rubber.
 8. The ballistic resistant fabric of claim1 wherein said polymeric binder material comprises a blend of a nitrilerubber polymer and a fluorine-containing material.
 9. The ballisticresistant fabric of claim 8 wherein the fluorine-containing materialcomprises from about 5 wt. % to about 20 wt. % of said polymeric bindermaterial.
 10. The ballistic resistant fabric of claim 1 wherein saidpolymeric binder material further comprises at least one surfactant. 11.The ballistic resistant fabric of claim 1 wherein said non-woven fabriccomprises a plurality of fiber plies wherein each fiber ply comprises aplurality of unidirectional fibers arranged in a substantially parallelarray, and wherein each of said fiber plies are cross-plied at an anglerelative to the fiber direction of each adjacent fiber ply.
 12. Aballistic resistant article formed from the ballistic resistant fabricof claim
 1. 13. A method of producing a ballistic resistant fabric, themethod comprising either step I) or step II), wherein: I) applying apolymeric binder material onto a plurality of fibers and thereafterforming a non-woven fabric from said fibers; said fibers having atenacity of about 7 g/denier or more and a tensile modulus of about 150g/denier or more; wherein said polymeric binder material comprises anitrile rubber polymer, said binder being resistant to dissolution,penetration and/or transpiration by water and resistant to dissolution,penetration and/or transpiration by one or more organic solvents,wherein the nitrile rubber polymer has an acrylonitrile content of fromabout 15 wt % to about 50 wt % and which polymeric binder materialcomprises from about 2% to about 50% by weight of the fabric; or II)organizing a plurality of fibers into at least one fiber layer,thereafter combining the at least one fiber layer with a polymericbinder material to form a non-woven fabric; said fibers having atenacity of about 7 g/denier or more and a tensile modulus of about 150g/denier or more; wherein said polymeric binder material comprises anitrile rubber polymer, said binder being resistant to dissolution,penetration and/or transpiration by water and resistant to dissolution,penetration and/or transpiration by one or more organic solvents,wherein the nitrile rubber polymer has an acrylonitrile content of fromabout 15 wt % to about 50 wt % and which polymeric binder materialcomprises from about 2% to about 50% by weight of the fabric.
 14. Themethod of claim 13 wherein step I) is conducted.
 15. The method of claim13 wherein step II) is conducted.
 16. The method of claim 13 wherein thepolymeric binder material comprises a blend of a nitrile rubber polymerand a fluorine-containing material.
 17. The method of claim 13 whereinsaid nitrile rubber polymer comprises a nitrile rubber terpolymer.
 18. Apolymer composition comprising a blend of at least one afluorine-containing material and at least one nitrile rubber terpolymer.19. The polymer composition of claim 18 wherein the nitrile rubberterpolymer has an acrylonitrile content of from about 15 wt. % to about50 wt. %.
 20. The polymer composition of claim 18 wherein said nitrilerubber terpolymer comprises a terpolymer formed from an acrylonitrilemonomer, a butadiene rubber and N-methylol acrylamide.
 21. The polymercomposition of claim 18 wherein said nitrile rubber terpolymer comprisescarboxylated nitrile rubber.
 22. The polymer composition of claim 18wherein the fluorine-containing material comprises from about 5 wt. % toabout 20 wt. % of said polymer composition.
 23. The polymer compositionof claim 18 which further comprises at least one surfactant.
 24. Thepolymer composition of claim 18 wherein said fluorine-containingmaterial comprises a chlorotrifluoroethylene homopolymer, achlorotrifluoroethylene copolymer, an ethylene-chlorotrifluoroethylenecopolymer, an ethylene-tetrafluoroethylene copolymer, a fluorinatedethylene-propylene copolymer, perfluoroalkoxyethylene,polychlorotrifluoroethylene, polytetrafluoroethylene, polyvinylfluoride, polyvinylidene fluoride, fluorocarbon-modified polyethers,fluorocarbon-modified polyesters, fluorocarbon-modified polyanions,fluorocarbon-modified polyacrylic acid, fluorocarbon-modifiedpolyacrylates, fluorocarbon-modified polyurethanes, perfluoroacrylate-modified polymers, perfluoroalkyl acrylic copolymerizates orcopolymers or blends thereof.
 25. The polymer composition of claim 18wherein said nitrile rubber polymer is uncured.